Residue and dietary exposure risk assessment of pyraclostrobin and tebuconazole in peach

To evaluate the dietary exposure risk of pyraclostrobin and tebuconazole in peach, supervised residue trials were carried out in eight typical regions, and the terminal residues of the two pesticides at harvest period were studied. A method for residue analysis of pyraclostrobin and tebuconazole in peach was revised and developed using high performance liquid chromatography-triple quadrupole mass spectrometry (HPLC-MS/MS). The results showed that there was a good linear relationship between the concentration and peak area of pyraclostrobin and tebuconazole in the range of 0.01-4.0 mg/L (R²≥0.9906). At the spiking levels of 0.01-4.0 mg/kg, the recoveries of pyraclostrobin were 88%-92% with the relative standard deviations (RSDs) of 5.6%-18.7%, and the recoveries of tebuconazole were 96%-106% with the RSDs of 0.8%-13.2%. The half-lives of pyraclostrobin and tebuconazole in peach fruits were 7.3-13.9 d and 5.4-8.9 d, respectively. The supervised trial median residues (STMR) of pyraclostrobin and tebuconazole in whole fruit of peach were 0.037 and 0.053 mg/kg, and the highest residues (HR) were 0.16 and 0.24 mg/kg, respectively. At 28 d after the last application, the contribution (RQc) of residues of pyraclostrobin and tebuconazole in peaches to the risk quotient (RQ) were 0.02% and 0.03%,respectively, which indicated that the chronic dietary exposure risk of pyraclostrobin and tebuconazole in peach to the general population in China was very low. For the short-term dietary exposure risk assessment, the national estimated short-term intake (NESTI) of pyraclostrobin and tebuconazole accounted for 0.4% and 2% of the acute reference dose (ARfD) respectively, and it was 2% and 4% for children aged 1-6 years, which indicated that the acute exposure risk was also at an acceptable level. Overall, based on the supervised residue trials and the long-term and short-term dietary exposure risk analysis, it could be considered that pyraclostrobin and tebuconazole are safe to be applied strictly in accordance with the Good Agricultural Practices and label recommendations on peach trees.